stackOnTop.swift

import Foundation


class Rod {
    
    fileprivate var stack = [Int]()
    
    public func stackOnTop(diskSize newDiskSize: Int) throws {
        if let topDiskSize = stack.popLast() {
            guard topDiskSize > newDiskSize else {
                throw RodSizeError.RodSizeIsTooHigh(topDiskSize: topDiskSize, diskToBeInsertedSize: newDiskSize)
            }
        }
        stack.append(newDiskSize)
    }
}